The invention relates to a spray arrangement having at least one return flow nozzle for injecting liquid into a process environment, having a storage tank for the liquid to be injected, at least one return flow nozzle, at least one feed line from the storage tank to the at least one return flow nozzle, at least one pump in the feed line, at least one return line from the return flow nozzle to the storage tank and at least one regulating valve for regulating a liquid quantity injected by the at least one return flow nozzle.
Spray arrangements having return flow nozzles have the advantage that the liquid quantity injected can be regulated in a simple manner via the quantity of liquid flowing in the return line. Such spray arrangements are used for gas scrubbing or for gas cooling, for example, in which case the spray arrangement injects liquid into a process chamber, e.g. into a gas cooler, by means of a plurality of return flow nozzles. In order to avoid disadvantageously affecting sections of the plant which follow on downstream from the process chamber or the gas cooler, the liquid quantity injected must be set in such a way that the liquid injected is completely vaporized at the outlet of the gas cooler. This requires regulation of the liquid quantity injected. The disadvantage with spray arrangements having return flow nozzles is that, in the regulated range, more liquid must be supplied in the feed line than is injected by the return flow nozzle. Only when the maximum possible amount of liquid is injected, i.e. when the return line is closed, does the quantity of liquid fed in correspond to the quantity of liquid injected. If less than the maximum possible liquid is injected, it is even necessary to feed in more liquid via the feed line than corresponds to the maximum possible liquid quantity injected. The volume flow ratio of the quantity of water to be delivered by the pump in the case of maximum injection to the quantity of water to be delivered by the pump at minimum injection is normally in a range of from 1.3 to 1.7. For the design of the return flow nozzle system, this means that the delivery pump has to be designed for a volume flow which is 30% to 70% higher than is required for maximum injection, that the electric components for safeguarding and switching and the cable cross sections for supplying the motors of the delivery pumps have to be configured for the power required at the large quantity of water to be delivered at minimum injection, and that the pipes for the feed line and the return line have to be designed for a volume flow 30% to 70% higher than is required for maximum injection.
By means of the invention, the intention is to improve a spray arrangement having at least one return flow nozzle and to improve a method for operating a spray arrangement of this kind.
According to the invention, a spray arrangement having at least one return flow nozzle for injecting liquid into a process environment is provided for this purpose, said spray arrangement having a storage tank for the liquid to be injected, at least one return flow nozzle, at least one feed line from the storage tank to the at least one return flow nozzle, at least one pump in the feed line, at least one return line from the return flow nozzle to the storage tank and at least one regulating valve for regulating a liquid quantity injected by the at least one return flow nozzle, wherein at least one further nozzle is provided, which is connected to the feed line by means of a controllable valve for enabling and shutting off a liquid feed.
Since, in addition to the at least one return flow nozzle, at least one further nozzle is provided, which can be connected or disconnected by means of a controllable valve, it is possible to design the pumps and the pipes and the electrical equipment of the spray arrangement exclusively for the quantity of water injected at maximum injection. This is because maximum injection is achieved not by means of the at least one return flow nozzle alone but by means of the return flow nozzle operated in a closed circuit and the at least one further nozzle connected. If the return flow nozzle is then operated in the regulated range, i.e. at less than the maximum possible injection, the liquid quantity to be delivered in the feed line by the pump does admittedly increase. However, since the maximum injection of the return flow nozzle is lower than with conventional spray arrangements by the amount of injection effected by the further nozzle, the liquid quantity to be delivered in the feed line in the regulated range does not exceed the maximum required injection of the overall spray arrangement. The pumps, pipes and the electrical equipment of the spray arrangement according to the invention can thus be designed for the maximum required injection of the overall spray arrangement. Compared with conventional spray arrangements which use only regulatable return flow nozzles, this allows considerable savings.
Moreover, the combination of at least one return flow nozzle operated from maximum to minimum injection over its full regulated range with at least one further, connectable nozzle enhances the regulating ratio of the overall spray arrangement. Once the at least one return flow nozzle has reached its maximum injection, i.e. its return is closed, one or a plurality of cascaded further nozzles can be connected if more liquid is to be injected. Since fewer regulated return flow nozzles are required than with conventional systems, the liquid quantity to be delivered for minimum injection is reduced. The start-up behaviour of the spray arrangement is thereby likewise improved.
As a development of the invention, the at least one further nozzle is designed as a single-substance nozzle.
By means of a single-substance nozzle, a similar or even identical spray behaviour to that with return flow nozzles can be achieved. For example, the single-substance nozzles are designed as return flow nozzles but are not connected to the return line. In this way, an identical spray pattern can be achieved without problems in the case of the return flow nozzles and the further nozzles.
As a development of the invention, the at least one further nozzle is provided with an air-cleaning device.
It has proven advantageous to air-clean the at least one further nozzle in the disconnected state, e.g. by means of compressed air. Deposits in the further nozzle in the disconnected state are thereby avoided. More specifically, an air-cleaning device eliminates manual emptying of the nozzle, e.g. by removal of the spray lance and subsequent air-cleaning.
As a development of the invention, a compressed air source is provided, which can be connected to the at least one further nozzle by means of a switchable valve. In this way, the further nozzles can be air-cleaned without problems. As a result, no liquid remains within the further nozzles in the disconnected state thereof, thus eliminating the risk of encrustation.
The problem underlying the invention is also solved by a method for operating a spray arrangement according to the invention, in which liquid is injected into the process environment exclusively via the at least one return flow nozzle in a first operating range, and in which liquid is injected both by means of the at least one return flow nozzle and also by means of the at least one further nozzle in a second operating range.
Thus, since one or more further nozzles are connected in order to increase the injected liquid quantity in steps, the pumps, the pipe cross sections and the electrical equipment of the spray arrangement according to the invention have to be designed only for the liquid quantity which is required for maximum injection by the overall spray arrangement. Compared with conventional spray arrangements, which operate exclusively with return flow nozzles, it is thereby possible to achieve considerable savings.
As a development of the invention, regulation of a first liquid quantity in the first operating range in accordance with a predetermined liquid quantity to be injected is provided.
In a first operating range, which lies between a minimum possible injection and a maximum injection achievable by means of the at least one return flow nozzle, the liquid quantity injected can be regulated by means of the return flow nozzles.
As a development of the invention, connection, unregulated operation and/or disconnection of the at least one further nozzle in the second operating range is provided.
The second operating range lies between the maximum injection which can be achieved by means of the at least one return flow nozzle and the maximum injection of the overall spray arrangement. In this second operating range, at least one further nozzle or a plurality of further nozzles is connected to achieve a predetermined liquid quantity to be injected. Connection is advantageously performed in a cascaded manner in order to achieve a stepwise increase or decrease in the overall liquid quantity injected. A significant advantage here over conventional spray arrangements which operate exclusively with return flow nozzles is that the further nozzles are simply connected and then operated or disconnected in an unregulated manner. The liquid quantity fed to the further nozzles is thus injected completely into the process environment. If finer graduation of the liquid quantity injected is required in the second operating range than is obtained by connecting or disconnecting the further nozzles, regulation of the liquid quantity injected is possible by means of the return flow nozzles in the second operating range as well. As a liquid quantity injected is ramped up, for example, the return flow nozzle is first of all adjusted to its maximum possible injection by closing the return of the return flow nozzle. At least one further nozzle is then connected, resulting in a stepwise increase in the liquid quantity injected by the overall spray arrangement. If the liquid quantity injected is then to be regulated, this can be accomplished by a regulating mode of the return flow nozzle.
As a development of the invention, a plurality of further nozzles is provided, and, in the second operating range, connection, unregulated operation and/or disconnection of a number of further nozzles takes place in accordance with a predetermined liquid quantity to be injected.
In the case of a plurality of further nozzles, these can be connected or disconnected in cascade-fashion in order to achieve a predetermined liquid quantity to be injected.
As a development of the invention, regulation of a liquid quantity injected by means of regulation of the at least one return flow nozzle is provided in the second operating range.
In this way, regulation of the liquid quantity injected can also be accomplished in the second operating range. This is preferred if graduation through connection or disconnection of the at least one further nozzle provides graduation that is too coarse for satisfactory operation of the spray arrangement.
As a development of the invention, air-cleaning of the at least one further nozzle after disconnection is provided.
In this way, encrustations or blockages of the at least one further nozzle can be prevented when the latter is disconnected and thus not in operation.